The present invention relates to an auto leveling apparatus of vehicle headlamp which automatically adjusts the inclination of a light axis of a headlamp (hereinafter referred to as auto leveling), on the basis of the inclination of a vehicle in the front and back direction (hereinafter referred to as a pitch angle), in the direction canceling the pitch angle, and particularly to an auto leveling apparatus which automatically adjusts the inclination of a light axis of a headlamp up and down on the basis of a pitch angle of a vehicle that is stopping.
A headlamp used in an auto leveling apparatus is so structured that a reflector into which a light source is attached is supported tiltably about a horizontal tilting axis in relation with respect to a lamp body and a light axis of the reflector (headlamp) can be tilted about the horizontal tilting axis by an actuator.
The conventional auto leveling apparatus is so structured that a pitch angle sensor, a speed sensor, a controller for controlling drive of an actuator on the basis of these detection signals, and the like are provided for a vehicle and the light axis of the headlamp (reflector) is adjusted so as to always become constant in relation to a road surface.
In case that according to the vehicle posture change caused by acceleration and deceleration during running of a vehicle or according to the load change caused by loading and unloading of goods or by getting on and off of passengers during stopping of the vehicle, the actuator is driven on a real time regardless of running or stopping of the vehicle and leveling is performed, the number of operations of the actuator is very large and the consumed power increases. Further, in such a case, drive mechanism components such as a motor, a gear, and the like require large durability, so that increase in cost is caused. Therefore, in order to decrease the number of drives of the actuator and provide at a low cost an auto leveling apparatus that can be used for a long time, an auto leveling apparatus (U.S. Pat. No. 6,183,118 or the like) has been proposed, which controls the drive of the actuator at regular intervals (for example, at intervals of 10 seconds) during the stoppage.
However, in the conventional auto leveling apparatus, the drive of the actuator is controlled on the basis of pitch angle data previously detected according to the interval time (for example, intervals of 10 seconds). Therefore, even if there is no change of static loading caused by getting on and off, since the light axis adjustment is performed according to the road surfaces, the number of operations of the actuator increases correspondingly thereby to cause a problem of a lowering of an actuator""s life.
The invention has been made in view of the problem of the related art, and its object is to drive the actuator only in case that the vehicle posture that has changed once during stoppage becomes stable and its stable vehicle posture is different from a vehicle posture immediately after stoppage or a vehicle posture controlled at the last time thereby to decrease the number of operations of the actuator in the auto leveling apparatus as much as possible.
In order to achieve the object, according to the first aspect of the invention, an auto leveling apparatus of vehicle headlamp comprises: a headlamp of which a light axis tilts up and down in relation to a car body by drive of an actuator; a control unit for controlling the drive of the actuator; a speed sensor for detecting car speed; a pitch angle sensor for detecting car pitch angle; and a memory for storing the car pitch angle data detected by the pitch angle sensor, in which the control unit controls the drive of the actuator, on the basis of the pitch angle data detected by the pitch angle sensor, so that the light axis of the headlamp has the fixed inclination in relation to a road surface, the control unit controls the drive of the actuator only in case that a vehicle posture (pitch angle data) that has changed once during stoppage becomes stable and the difference between its stable vehicle posture and a reference posture (reference pitch angle data) exceeds the predetermined value.
Whether the vehicle is stopping or not is judged by the control unit on the basis of outputs detected by the speed sensor.
Further, regarding the stability of the vehicle posture (pitch angle data) that has changed once, as described in the second aspect of the invention, the control unit finds by the operation average pitch angle data on plural different moving times (moving time average pitch angle data), and in case that these data are nearly the same, the control unit judges the vehicle posture to become stable.
Namely, under the condition where static loading applied onto the vehicle is changing such as in case that passengers are getting on and off the vehicle, the detected pitch angle data changes momentarily and is not constant. On the other hand, under the condition where the constant static loading is applied onto the vehicle, the vehicle posture becomes stable and the detected pitch angle data becomes a constant value. Therefore, average pitch angle data on plural different moving times (moving time average pitch angle data), such as 1 sec. average pitch angle data and 3 sec. average pitch angle, are taken, and these data are compared with each other. In case that there is difference between the data, it is found that the vehicle posture does not become stable, and in case that there is no difference, it is found that the vehicle posture becomes stable. Therefore, in the invention, stability of the vehicle posture that is a condition necessary to drive-control the actuator is judged by whether there is difference between the average pitch angle data on the plural different moving times (moving time average pitch angle data).
Further, whether there is difference between the present posture and the original reference posture (reference pitch angle data) or not is judged by comparison between the present posture (pitch angle data) and the reference posture as a general rule. However, there is no corresponding reference posture before the first drive control of the actuator is executed. Therefore, as described in the third aspect of the invention, in a first actuator drive control after stoppage, the detected posture (moving time average pitch angle data) is compared with a posture immediately after stoppage (moving time average pitch angle data), and in an actuator drive control from the second on, the detected posture (1 sec. average pitch angle data) is compared with the posture (pitch angle data) used in the last actuator drive, whereby whether the posture becomes stable or not is judged. (Working) Since the drive of the actuator is controlled only during stoppage, the number of operations of the actuator is reduced correspondingly.
Further, since the actuator is not driven every time the posture changes but it is driven only in case that the posture becomes stable (since it is not driven before the posture does not become stable), the number of operations of the actuator is reduced correspondingly.
Further, during stoppage, even if the posture that has changed once becomes stable, as long as there is not difference over the predetermined value between the stabilized posture and the reference posture, the actuator is not driven. Therefore, the number of operations of the actuator is reduced correspondingly.
Since the number of operations of the actuator is thus reduced, the consumed power is saved and the wear of drive mechanism components of the actuator is reduced.